The National Rifle Association, or the NRA, is America's biggest nonprofit organization advocating gun rights. It was established in the 19th century, and many former presidents of the US have been members of the organization. David Keene was the NRA's president from 2011 to 2013. He successfully led the organization in foiling attempts by the US government to control guns.

The Second Amendment to the US Constitution was adopted in 1791. It protects the right of the people to keep and bear arms. At the NRA headquarters, the only place open to the public is a museum of firearms. And a copy of the Second Amendment is proudly displayed at the museum.

But circumstances have changed with the passage of time. The second amendment was adopted more than 200 years ago..and has become controversial in today's modern world. 

Although the Supreme Court made the final decision in the landmark case of District of Columbia v. Heller, it didn't end the controversy. More debates are still raging on.

In Obama's terms, the US government has put in place the strictest-ever gun control measures, including background checks for all gun-buyers. But in the face of resistance from organizations such as the NRA, the White House has failed to enhance such controls through legislation.

"Guns don't kill people, people kill people" That's the NRA's most famous slogan. Some people may say it sounds reasonable, but frequent attacks have prompted many others to question it.

And with mass shootings becoming a regular event in the US, the debate is expected to rage on for some time to come.